The present invention relates to an airbag device, and more particularly, to an airbag device which can be suitably applied to an airbag device for a front passenger""s seat (hereinafter, referred to as xe2x80x9cpassenger airbag devicexe2x80x9d) which is installed in an instrument panel of a vehicle. More particularly, the present invention relates to an airbag device in which a casing is provided with plate members, such as thick plates, fixed thereto and a lid engaging the plate members. The present invention also relates to a casing used for this airbag device.
One of known passenger airbag devices is a passenger airbag device in which thick plates are attached to a casing, and a lid is engaged with the thick plates by hooks of the thick plates.
FIG. 7 is a sectional view showing a conventional airbag device. This airbag device 1 comprises an inflator 2 for generating gas in the event of a vehicle collision, a casing 3 for accommodating the inflator, an airbag 5 folded and accommodated inside the casing 3, and a lid 6 for closing an upper opening of the casing 3. The airbag device 1 is installed in an instrument panel 9 of a vehicle. Fixed to upper outer surfaces of the casing 3 by spot welding are thick plates 10, 11. The thick plates 10, 11 extend along the upper edges of the casing 3. A plurality of claw-like hooks 12 is formed integrally with the thick plates 10, 11 and spaced apart from each other at suitable intervals in the longitudinal directions of the thick plates 10, 11. Legs 7 of the lid 6 are formed with holes 13, located corresponding to the hooks 12, in which the hooks 12 are fitted, respectively. The lid 6 is provided with a reduced wall portion 8 formed in the inner surface thereof.
To attach the lid 6 to the casing 3 for assembling the airbag device 1, the lid 6 is pressed in such a manner as to close the upper opening of the casing 3. Then, the legs 7 of the lid 6 are elastically deformed outwardly to pass over the hooks 12. At portions where the hooks 12 and the holes 13 are met to each other, the legs 7 return to the original configuration, whereby the hooks 12 engage the inner edges of the holes 13.
In the airbag device structured as mentioned above, as the inflator 2 is actuated, the airbag 5 is inflated and the lid 6 is torn along the reduced wall portion 8, thereby allowing the airbag 5 to deploy into the vehicle cabin.
The thick plates 10, 11 are attached to the casing 3 and the lid 6 is engaged with the hooks of the thick plates 10, 11, so that the required strength of the casing 3 can be reduced, thereby achieving the reduction in thickness and weight of the casing 3.
In the aforementioned conventional airbag device shown in FIG. 7, the spot welding is required to connect the thick plates 10, 11 to the casing 3 at a large number of points, thereby requiring a lot of works for connecting the thick plates 10, 11 to the casing 3 and increasing the manufacturing cost of the casing 3. In this case, when the number of the points to be welded is reduced, the reduction in thickness of the casing 3 can not be made because the impact load applied to the thick plates 10, 11 when the lid 6 is opened by the inflation of the airbag 5 is received by the welded portions where the number is reduced. During the inflation of the airbag 5, a force for enlarging the upper portion of the casing 3 is applied by the airbag 5. With the reduced number of the welded portions, the reinforcement effect of the thick plates 10, 11 is not enough. This is because the portions of the casing 3 corresponding to the end portions of the thick plates 10, 11 without the welded portions are largely deformed, so that the deformation of the casing 3 is increased.
The object of the present invention is to solve the aforementioned problems, and to provide an airbag device which allows easy fixing of plate members, such as thick plates, to a casing and provides large reinforcement effect for the casing by the plate members.
An airbag device of the present invention comprises a casing having an opening in the top thereof, an airbag accommodated in the casing and connected to the casing, a gas generator for supplying gas into the airbag to inflate the airbag, plate members fixed to side walls of the casing, and a lid engaging the plate members to cover the opening. At least parts of the plate members are disposed inside the side walls of the casing.
A casing of the present invention accommodates an airbag and includes plate members disposed along edges of an opening of the casing. At least parts of the plate members are disposed inside the casing.
In the present invention, it is preferable that the plate member has a thickness larger than that of the casing, or is provided with a rib to have rigidity higher than that of the casing.
According to the airbag device as mentioned above, at least parts of the plate members are disposed inside the casing, so that a pressure applied to the casing by the inflation of the airbag acts in such a direction as to press the plate members to the casing. Therefore, even with reduced number of the welded portions between the plate members and the casing, the plate members can prevent the deformation of the casing.
In this case, the plate members have hooks for engaging the lid, and the ends of the hooks project outside of the casing through holes formed in the casing, respectively. Thus, stress applied to the thick plates is transmitted not only to the welded portions between the thick plates and the casing but also to the casing via contacts between the upper edges of the holes and the hooks, so that the stress is widely dispersed and transmitted to the casing.
In the present invention, it is preferable that the plate members extend in the longitudinal direction of the edges of the opening. It is preferable that a plurality of the hooks is disposed to be spaced at intervals in the longitudinal direction of the plate members and the hooks are engaged with the holes formed in the lid.
According to the present invention, the height, i.e. the length in the vertical direction, of the holes at both ends in the longitudinal direction may be larger than the height of the holes arranged between the holes at both ends. By this structure, the deformation of the casing when a passenger collides with the lid is increased, thereby improving the absorption of the impact